1. Field of the Invention
This invention relates to an apparatus for driving cutting tools radially in a lathe. More particularly, it is concerned with an improvement in the driving apparatus comprising a pair of oppositely disposed tool rests mounted on a slider, and between which work is positioned.
2. Description of the Prior Art
Oppositely disposed tool rests for an automatic lathe having a movable headstock are known, as they are, for example, disclosed in U.S. Pat. No. 3,811,346 to Takayuki Nomura. Referring to FIG. 1 (prior art), a frame 2 secured to a bed 1 supports a slider 3 which is slidable radially of work W. A pair of tool rests 6a and 6b are disposed opposite to each other in the slider 3, and the work W is positioned between the tool rests. The slider 3 is driven by a servo motor 4 and a ball screw and nut assembly 5 to move the tool rests radially of the work W.
In the apparatus as hereinabove described, it is better to shorten the traveling stroke of the cutting tools, hence the slider 3 as far as possible in order to reduce the overall size of the machine, and the time required for changing the cutting tools. This consideration, however, brings about a disadvantage when one of the tool rests 6a and 6b is replaced by a milling or cross drilling device which requires a considerably greater stroke of movement. The stroke of movement designed for the tool rests 6a and 6b is not sufficient for the movement of the cutting tools in the milling or drilling device. If the slider 3 is designed for movement over a greater distance to suit the milling or drilling device, the cutting tool on the remaining tool rest moves along an unnecessarily long distance.